Add Two Numbers (Medium)

Description

You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

Analysis

链表模拟

My Solution

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//C++
/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
        int mod = 0 , flag = 0,x,y;
        ListNode *head , *p=NULL;
        while(l1||l2){
            if(l1==NULL) x = 0;
            else {
                x = l1->val;
                l1 = l1->next;
            }
            if(l2==NULL) y = 0;
            else {
                y = l2->val;
                l2 = l2->next;
            }
            if(flag == 0){
                head = p = new ListNode((x+y+mod)%10);
                mod = (x+y+mod)/10;
                flag = 1;
            }
            else{
                p->next = new ListNode((x+y+mod)%10);
                mod = (x+y+mod)/10;
                p = p->next;
            }

        }
        while(mod){
            p->next = new ListNode(mod%10);
            mod/=10;
            p = p->next;
        }
        return head;
    }
};